1. Field of Invention
The invention relates to a device for transmitting and/or storing texture signals available in the form of digital signals corresponding to the luminosity of the pixels of a picture, and to a device for synthesizing texture signals for such a transmitting and/or storage device. The invention also relates to a system transmitting and/or storing texture signals corresponding to at least partly textured pictures. Herein, texture to be understood to mean a picture area of homogeneous appearance, even if it is not strictly uniform. Such an invention is suitable for all uses where video information compression is employed, particularly in products such as CD-I, Minitel, videophones or digital video recorders, as well as high-definition television or medical imaging.
2. Description of the Related Art
For transmission and/or storage of image data it is often necessary to reduce the amount of such data. Currently used data compression methods treat the picture as a collection of two-dimensional data signals without any further assumptions being made as to the nature of these signals. For example, in accordance with one method the picture is subdivided into regular blocks each having therein a given number of picture elements (or pixels), and the data signals corresponding to these blocks are subjected to an orthogonal transform and subsequently to a variable-length coding. U.S. Pat. No. 4,394,774 describes a digital data compression system which uses such a method and which thus enables signals corresponding the original signals to be subsequently reconstituted from the compressed signals by minimizing an average error criterion per block. However, such an approach, which is satisfactory at high bit rates (approximately 1 bit per pixel), is not suitable at lower bit rates because latent artifacts appear such as block effects or blurring due to removal of the high frequencies.
Therefore, it is an object of the invention to provide a device which, on the contrary, allows for the pixel data signals to be transmitted and/or stored in a manner which enables a specific coding method to be used which is very economical both as regards the amount of transmitted data and the computing time, and which allows the original data signals to be recovered as reliably as with prior techniques.